The present invention is directed to bicycles and, more particularly, to a circuit that receives signals from a dynamo and provides signals for charging a battery and indicating bicycle speed.
Bicycles often are equipped with dynamos for powering headlights and other types of lights. Contemporary bicycles, however, are equipped not only with such lights but also with actuators for operating electrically driven shifters, actuators for adjusting the dampening force of an electrically driven suspension, indicator backlights for cycle computers, and the like. Such equipment will be referred to below as “electrically driven units”, and they also receive their power from the dynamo. These electrically driven units begin operating unstably when their electric drive voltage falls below a specific level, so some accommodation must be made for supplying stable electric drive voltage to them. In late-model bicycles, a dynamo charges a secondary battery which, in turn, powers the electrically driven units. Because stable electric drive voltage is needed to energize such electrically driven units in the above-described manner, the present inventor has already devised and proposed an apparatus that allows the charging voltage to be detected and a stabilized charging voltage to be obtained through appropriate switching of the dynamo output.
Speedometers are sometimes mounted on bicycles. Such speedometers operate with speed detection signals such as signals from a sensor that senses signals from a magnet mounted to the bicycle wheel. A technique for retrieving speed detection signals from a dynamo output is disclosed in JP (Kokai) 7-229909. However, when the dynamo output is switched in a controlled manner in order to control the charging voltage, the voltage drop varies significantly because of the presence of a load resistance, an impedance or inductance in the dynamo, or the like. The switching also induces substantial disruptions in the output waveform of the dynamo. Low-pass filters and other circuits are needed in order to obtain a speed detection signal from a signal whose waveform is markedly disrupted in this manner, thus increasing the size and cost of the device.